Analysis of Open and Torsen Differential

1
Analysis of Open and Torsen Differential

• Group Members
• Scott Anderson
• Michael Bullard
• Jason Yount

2
Differential Overview

• When turning, the inner and outer wheels have
  arcs of different turning radii
• Consequently, the inner wheels travel less
  distance than the outer wheels

3
Differential Overview

• Because the turning paths of the inner and outer
  wheels are different, the wheels on both axles
  need to be able to spin independently of each
  other
• A differential is used to allow the wheels to
  spin at different speeds

4
Different Types of Differentials

• Open Differential
• Limited Slip Differential (LSD)
• Clutch LSD
• Viscous Coupling LSD
• Locking LSD
• Torsen LSD

5
Schematic of an Open Differential

• The Sun gear and Ring gear are identical and
  supply power to the drive axles.
• The planetary gears, or spider gears allow the
  axles to rotate at different speeds.

6
Open Differential

• The open Differential is a planetary gear set.
  Therefore the following equation applies

7
Open Differential

• The number of teeth on the ring gear and sun gear
  are equal and the planetary gear formula is
  simplified
• The angular velocity of the differential is equal
  to the average angular velocity of the axles

8
Open Differential Problems

• As a result, if one wheel has little friction
  there is no resistance to its rotation and
  slipping occurs
• The slipping wheel will spin twice as fast as the
  differential

Left rear tire slipping on sandy surface
9
The Torsen Differential

• The Torsen Differential is capable of perfect
  differentiation
• The Torsen Differential transfers power to the
  wheels with traction

Torque transferred to wheel with traction
10
How the Torsen Differential Works

• Power is transferred from the engine to the
  differential housing causing the housing to turn
• Power flows from the housing to the worm wheels
  attached to the housing
• The worm wheels are meshed with the worm gears
  attached to the axles which turns the axle with
  the differential housing

11
Differential Function

• When turning, the outer wheel turns at a high RPM
  with respect to the differential housing
• Therefore, the outer wheel axle turns its worm
  gear and its mating worm wheel
• The mating worm wheels are meshed together by
  spur gears
• Perfect Differentiation as one wheel increases
  speed the other wheel decreases speed
  proportionally
• Torque is maintained at both wheels while
  cornering

12
Traction Loss By One Wheel

• Spinning wheel turns its worm gear which turns
  its mating worm wheel
• Mating worm wheel wants to turn opposite worm
  wheel
• Opposite worm wheel transfers power to opposite
  worm gear

13
Traction Loss By One Wheel

• Opposite worm gear is attached to the axle of the
  wheel with traction
• The slipping wheel does not spin
• Torque is transferred to the wheel with traction

14
Torque Transfer

• The torque bias ratio determines the amount of
  torque transferred and is dependant on the gear
  design
• 51 ratio transfers 5 times the torque to the
  wheel with traction
• If one wheel loses all traction no torque is
  transferred to the wheel with traction

Torque transferred to wheel with traction
15
Application of Torsen Differentials

• Torsen differentials are used in off-road and
  high performance all-wheel drive vehicles.
• Torsens can also be handy on icy or dirt roads

16
Automobile Companies Using the Torsen Differential

• AM General
• Audi
• BMW
• Ford
• GM
• More specific details at http//www.torsen.com/oem
  .htm

• Honda
• Lexus
• Land Rover
• Mazda
• Toyota
• Volkswagen

17
Companies Using Torsen Differential

• General Motors
• Camaro SS 1998

• AM General
• Hummer

• Audi
• A4 Quattro

• BMW
• Z3